Area Forecast Discussion
Issued by NWS New Orleans/Baton Rouge, LA

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924
FXUS64 KLIX 230534
AFDLIX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NEW ORLEANS LA
1134 PM CST THU JAN 22 2015

.UPDATE...
WILL ALLOW THE WIND ADVISORY TO EXPIRE AT MIDNIGHT AS PLANNED AS
TROUGH AXIS MOVES THROUGH METRO AREA BY THEN. LIGHTNING COUNTS ARE
ALSO TRENDING DOWN THOUGH ONE OR TWO ISOLATED STRIKES MAY STILL
OCCUR OVER LAND AREAS OF THE SOUTH SHORE FOR ANOTHER 1-2 HOURS.

&&

.AVIATION...
IFR CONDITIONS IN RAIN WILL BE IMPROVING TO GENERAL MVFR CIGS AND
LIGHT FOG FROM WEST-EAST OVERNIGHT...THEN PREVAILING THROUGH END
OF TAF VALID PERIOD.

&&

.PREV DISCUSSION... /ISSUED 840 PM CST THU JAN 22 2015/

UPDATE...
NUMBER 2 TO INCREASE AREAL COVERAGE OF THUNDERSTORMS THROUGH
MIDNIGHT AS WARM SECTOR NUDGES FARTHER INLAND AND AIR MASS
DESTABILIZES FURTHER AS LOW PRESSURE AREA SKIRTS ALONG THE COAST
LATER TONIGHT. ALSO UPDATED WIND GRIDS FOR LATEST HI RES WRF
OUTPUT THAT SEEMS TO BE HANDLING THE SURFACE WIND DEPICTION PRETTY
WELL THOUGH MAYBE A TAD HIGH. TRIMMED BACK TO PREVIOS GRIDS FROM
06Z-12Z. NO OTHER CHANGES AT THIS TIME.  24/RR

PREV DISCUSSION... /ISSUED 747 PM CST THU JAN 22 2015/

UPDATE...
ISSUED A WIND ADVISORY FOR THE SOUTH SHORE PARISHES AS WIND GUSTS
WERE BECOMING FREQUENT IN THE 30-40 MPH RANGE AT KNEW AND KMSY.
THESE HIGHER GUSTS WILL LIKELY CONTINUE THROUGH MIDNIGHT AND
LESSEN AS THE WARM FRONT SURGES NORTHWARD TO THE TIDAL LAKES
AROUND THAT TIME. WARM FRONT NOTED AT MOUTH OF MS RIVER WHERE SOME
STRONG TURNING IS NOTED IN VAD WIND PROFILE AND SURFACE BASED
APPEARANCES OF CONVECTION THAT HAS RECENTLY ACQUIRED LIGHTNING.
HAVE INTRODUCED THUNDER FOR THE COASTAL WATERS AND AREAS NEAR THE
COAST FOR THE NEXT FEW HOURS.

MARINE...
SMALL CRAFT ADVISORY REMAINS IN EFFECT AS WIND GUSTS HAVE BECOME
QUITE PRONOUNCED THE PAST 1-2 HOURS. HAVE INTRODUCED TSRA AS
WEATHER DESCRIPTOR IN COASTAL WATERS WHERE ROTATING STORMS ARE
NOTED NEAR THE MOUTH OF THE MS RIVER AND A LINE OF THUNDERSTORMS
ALONG THE COLD FRONT SOUTHWEST OF THE LOW WHICH IS CURRENTLY SOUTH
OF MARSH ISLAND.

SOUNDING DISCUSSION...
WINDY LAUNCH THIS EVENING WITH GUSTS AROUND 25 MPH AT RELEASE IN
THE RAIN. A VERY SATURATED SOUNDING WITH PRECIPITABLE WATER NOW UP
TO 1.53 INCHES. SHALLOW COLD AIR NOTED BELOW INVERSION AT 1000FT
THAT WARMS TO A NOSE TEMP OF 13C AT 2800FT. RAINFALL PROCESS IS
ISENTROPIC IN NATURE WITH ELEVATED CONVECTIVE INSTABILITY ABOVE
800 MB. WINDS WERE NE 10-30KT BELOW 1KFT...E-SE 30-35 KT TO
5KFT...THEN SW THROUGH TROPOPAUSE AT 38KFT. 50 KT WINDS OBSERVED
13.7KFT AND PEAK WIND WAS 240/121KT AT 40.3KFT.

PREV DISCUSSION... /ISSUED 343 PM CST THU JAN 22 2015/

SHORT TERM...

A GULF LOW HAS BEGUN TO DEVELOP THIS AFTERNOON OVER THE WESTERN
GULF OFF THE COST OF TEXAS. THIS LOW WILL TRACK TO THE EAST-
NORTHEAST AND MOVE THROUGH THE NORTHERN GULF OF MEXICO JUST
OFFSHORE OF THE FORECAST AREA TONIGHT. IN THE UPPER LEVELS...A
STRONG UPPER LEVEL TROUGH IS CURRENTLY MOVING INTO TEXAS AND WILL
CONTINUE TO ADVANCE TOWARD THE LOWER MISSISSIPPI VALLEY TONIGHT
AND TOMORROW. OVERALL...STRONG FORCING WILL BE FOUND ACROSS THE
FORECAST AREA TONIGHT...AND EXPECT TO SEE A SHIELD OF MODERATE
RAINFALL OVERSPREAD THE ENTIRE FORECAST AREA. ALTHOUGH NOT
MENTIONED IN THE FORECAST...THERE COULD BE SOME ISOLATED
CONVECTION OVER THE OFFSHORE WATERS TONIGHT DUE TO SOME WEAK
INSTABILITY CURRENTLY IN PLACE OVER THAT REGION. QPF VALUES WILL
GENERALLY BE IN THE 1 TO 2 INCH RANGE...BUT SOME 3 INCH TOTALS
WILL BE POSSIBLE BY TOMORROW MORNING.

HEADING INTO TOMORROW...THE SURFACE LOW WILL BEGIN TO PULL EAST OF
THE REGION IN THE MORNING...BUT THE PARENT UPPER LEVEL TROUGH WILL
JUST BEGIN TO SWING INTO THE REGION. STRONG POSITIVE VORTICITY
ADVECTION AND AMPLE FORCING WILL REMAIN OVER THE AREA...AND EXPECT
TO SEE OVERCAST CONDITIONS AND SCATTERED TO NUMEROUS SHOWERS
LINGER THROUGH THE DAY. THE RAIN CHANCES WILL BE HIGHEST IN THE
MORNING...AS SOME DRIER MID-LEVEL AIR IS EXPECTED TO ADVECT INTO
THE AREA DURING THE AFTERNOON. HOWEVER...PW VALUES WILL REMAIN
ELEVATED THROUGH THE DAY...AND EXPECT SCATTERED SHOWERS TO BE IN
PLACE THROUGH THE EVENING HOURS. WITH THE MAIN HEART OF THE UPPER
LEVEL COLD POOL MOVING OVER THE AREA TOMORROW...TEMPERATURES WILL
BE WELL BELOW NORMAL WITH HIGHS GENERALLY IN THE 40S AND LOWER
50S.

RAIN CHANCES WILL BEGIN TO DECREASE RAPIDLY TOMORROW NIGHT...AS
DRIER AIR CONTINUES TO FEED INTO THE MID-LEVELS OF THE ATMOSPHERE
AND THE STRONGEST OMEGA SHIFTS TO THE EAST. HOWEVER...THERE SHOULD
CONTINUE TO BE SOME LINGERING SHOWER ACTIVITY OVER THE COASTAL
WATERS AND BENEATH THE HEART OF THE VORT LOBE OVER SOUTHERN
MISSISSIPPI THROUGH THE NIGHT. TEMPERATURES WILL ALSO COOL
SUBSTANTIALLY...AND EXPECT TO SEE LOWS IN THE MIDDLE 30S OVER MOST
OF THE FORECAST AREA BY DAYBREAK SATURDAY.

STRONG NEGATIVE VORTICITY ADVECTION AND SUBSIDENCE WILL BUILD OVER
THE REGION ON SATURDAY IN THE WAKE OF THE DEPARTING UPPER LEVEL
TROUGH. VERY DRY AIR WILL ALSO FEED INTO THE AREA...AND EXPECT TO
SEE RAPIDLY CLEARING SKIES SATURDAY MORNING. THESE CLEAR AND DRY
CONDITIONS WILL PERSIST INTO SUNDAY AS DEEP LAYER NORTHWEST FLOW
DOMINATES THE GULF SOUTH. THIS NORTHWEST FLOW WILL ALSO KEEP A
COOLER AIRMASS ADVECTING INTO THE REGION...AND EXPECT TEMPERATURES
TO AVERAGE ABOUT 10 DEGREES BELOW NORMAL FOR SATURDAY AND SUNDAY.

LONG TERM...

OVERALL...A VERY BENIGN WEATHER PATTERN IS EXPECTED FOR THE FIRST
HALF OF NEXT WEEK...AS A STRONG MID AND UPPER LEVEL RIDGE BUILDS
OVER THE REGION. CONTINUED SUBSIDENCE THROUGHOUT THE ATMOSPHERIC
COLUMN WILL KEEP CLEAR SKIES AND LOW HUMIDITIES IN PLACE.
TEMPERATURES WILL MODIFY SLOWLY THROUGH THE WEEK...WITH READINGS
RISING BACK TO MORE NORMAL LEVELS FOR TUESDAY AND WEDNESDAY.

AVIATION...

MVFR CEILINGS AND VISIBILITIES SHOULD FALL INTO IFR RANGE AFTER
00Z TONIGHT...AS A BAND OF MODERATE TO LOCALLY HEAVY RAINFALL
DEVELOPS OVER THE TERMINALS. THESE CONDITIONS WILL PERSIST THROUGH
AROUND 18Z TOMORROW...BEFORE IMPROVING BACK INTO MVFR RANGE DURING
THE AFTERNOON HOURS.  32

MARINE...

A STRENGTHENING GULF LOW CURRENTLY OVER THE WESTERN GULF WILL
SLIDE THROUGH THE COASTAL WATERS TONIGHT. STRONG GRADIENT FLOW OF
20 TO 25 KNOTS AND ROUGH SEAS OF 4 TO 9 FEET CAN BE EXPECTED AS
THIS LOW MOVES THROUGH. GIVEN THIS...SMALL CRAFT ADVISORIES ARE IN
PLACE FOR ALL OF THE WATERS TONIGHT. CONDITIONS WILL BRIEFLY
IMPROVE TOMORROW IN THE WAKE OF THE LOW...WITH WINDS AND SEAS
FALLING BACK INTO EXERCISE CAUTION RANGE. HOWEVER...AS THE MAIN
UPPER LEVEL TROUGH AND COLD FRONT SLIDE THROUGH TOMORROW
NIGHT...NORTHWEST FLOW OF 20 TO 25 KNOTS AND HIGHER SEAS OF 4 TO 8
FEET WILL REDEVELOP OVER THE COASTAL WATERS. THESE CONDITIONS WILL
PERSIST INTO SUNDAY MORNING BEFORE EASING. A REINFORCING FRONT
SLIDING THROUGH SUNDAY NIGHT WILL PUSH WINDS AND SEAS BACK TOWARD
SMALL CRAFT ADVISORY RANGE FROM LATE SUNDAY NIGHT INTO MONDAY.
CONDITIONS SHOULD EASE BACK BELOW ADVISORY RANGE MONDAY NIGHT AS A
SURFACE HIGH SETTLES INTO THE SOUTHEASTERN UNITED STATES. 32

DECISION SUPPORT...

DSS CODE...BLUE.
DEPLOYED...NONE.
ACTIVATION...NONE.
ACTIVITIES...SLURRY SUPPORT
             SMALL CRAFT ADVISORY

DECISION SUPPORT SERVICES (DSS) CODE LEGEND
GREEN  = NO WEATHER IMPACTS THAT REQUIRE ACTION
BLUE   = LONG FUSED WATCH/WARNING/ADVISORY IN EFFECT OR HIGH
         VISIBILITY EVENT
YELLOW = HEIGHTENED IMPACTS WITH SHORT FUSED
         WATCH/WARNING/ADVISORY ISSUANCES; RADAR SUPPORT
ORANGE = HIGH IMPACTS - SLIGHT TO MODERATE RISK SEVERE; NEARBY
         TROPICAL EVENTS; HAZMAT OR OTHER LARGE EPISODES
RED    = FULL ENGAGEMENT FOR MODERATE TO HIGH RISK SVR
         AND/OR DIRECT TROPICAL THREATS; EVENTS OF NATIONAL
         SIGNIFICANCE.

&&

.PRELIMINARY POINT TEMPS/POPS...
MCB  45  48  35  56 / 100  60  40   0
BTR  43  48  36  58 / 100  60  30   0
ASD  47  51  37  58 / 100  80  30   0
MSY  47  50  38  55 / 100  80  30   0
GPT  48  52  38  57 / 100  80  30   0
PQL  50  52  38  57 / 100  90  30  10

&&

.LIX WATCHES/WARNINGS/ADVISORIES...
LA...WIND ADVISORY UNTIL MIDNIGHT FRIDAY FOR THE FOLLOWING ZONES:
     LOWER JEFFERSON...LOWER PLAQUEMINES...LOWER ST.
     BERNARD...ORLEANS...UPPER JEFFERSON...UPPER
     PLAQUEMINES...AND UPPER ST. BERNARD.

GM...SMALL CRAFT ADVISORY UNTIL 6 AM FRIDAY FOR THE FOLLOWING ZONES:
     BRETON SOUND...CHANDELEUR SOUND...COASTAL WATERS FROM PORT
     FOURCHON TO LOWER ATCHAFALAYA RIVER FROM 20 TO 60
     NM...COASTAL WATERS FROM PORT FOURCHON TO LOWER ATCHAFALAYA
     RIVER OUT 20 NM...COASTAL WATERS FROM THE SOUTHWEST PASS OF
     THE MISSISSIPPI RIVER TO PORT FOURCHON FROM 20 TO 60
     NM...COASTAL WATERS FROM THE SOUTHWEST PASS OF THE
     MISSISSIPPI RIVER TO PORT FOURCHON OUT 20 NM...LAKE
     BORGNE...LAKE PONTCHARTRAIN AND LAKE MAUREPAS...AND
     MISSISSIPPI SOUND.

     SMALL CRAFT ADVISORY UNTIL NOON FRIDAY FOR THE FOLLOWING ZONES:
     COASTAL WATERS FROM BOOTHVILLE LA TO THE SOUTHWEST PASS OF
     THE MISSISSIPPI RIVER OUT 20 NM...COASTAL WATERS FROM
     PASCAGOULA MS TO STAKE ISLAND LA FROM 20 TO 60 NM...COASTAL
     WATERS FROM PASCAGOULA MS TO STAKE ISLAND LA OUT 20
     NM...AND COASTAL WATERS FROM STAKE ISLAND LA TO THE
     SOUTHWEST PASS OF THE MISSISSIPPI RIVER FROM 20 TO 60 NM.

MS...NONE.
GM...SMALL CRAFT ADVISORY UNTIL 6 AM FRIDAY FOR THE FOLLOWING ZONES:
     BRETON SOUND...CHANDELEUR SOUND...COASTAL WATERS FROM PORT
     FOURCHON TO LOWER ATCHAFALAYA RIVER FROM 20 TO 60
     NM...COASTAL WATERS FROM PORT FOURCHON TO LOWER ATCHAFALAYA
     RIVER OUT 20 NM...COASTAL WATERS FROM THE SOUTHWEST PASS OF
     THE MISSISSIPPI RIVER TO PORT FOURCHON FROM 20 TO 60
     NM...COASTAL WATERS FROM THE SOUTHWEST PASS OF THE
     MISSISSIPPI RIVER TO PORT FOURCHON OUT 20 NM...LAKE
     BORGNE...LAKE PONTCHARTRAIN AND LAKE MAUREPAS...AND
     MISSISSIPPI SOUND.

     SMALL CRAFT ADVISORY UNTIL NOON FRIDAY FOR THE FOLLOWING ZONES:
     COASTAL WATERS FROM BOOTHVILLE LA TO THE SOUTHWEST PASS OF
     THE MISSISSIPPI RIVER OUT 20 NM...COASTAL WATERS FROM
     PASCAGOULA MS TO STAKE ISLAND LA FROM 20 TO 60 NM...COASTAL
     WATERS FROM PASCAGOULA MS TO STAKE ISLAND LA OUT 20
     NM...AND COASTAL WATERS FROM STAKE ISLAND LA TO THE
     SOUTHWEST PASS OF THE MISSISSIPPI RIVER FROM 20 TO 60 NM.

&&

$$

24/RR






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